Development of a plant-based vaccine against malaria

Malaria is the most prevalent tropical human disease reported worldwide, caused by protozoan parasites. Half of the world's population is at risk of malaria, and more than 200 million new cases are reported annually. Currently, there are no licensed vaccines available for use. Therefore, there is a vital need for developing an effective and reliable anti-malaria vaccine ideally protecting different parasitic infection stages comprising different antigens that generate appropriate cell-mediated antibody responses of the parasite presentation. Plant-based vaccines serve as novel platforms for developing safe, reliable, and affordable treatments. In this study, a Malchloroplast candidate vaccine is designed, comprised of segments of AMA-1 and MSP-1 proteins along with the GK1 peptide form Teania solium as adjuvant, and expressed in tobacco chloroplasts. Transplastomic tobacco lines have been generated using biolistic transformation, and these are confirmed to carry the synthetic gene construct. The synthetic GK1 peptide is confirmed to be expressed using RT-PCR and Western blots, and detected by RP-HPLC at levels of up to 6 µg g-1 dry weight of tobacco leaf tissue. The plant-derived Malchloroplast candidate vaccine components have been recognized by antibodies in Plasmodium falciparum Malaria patients, and has elicited specific antibodies in subcutaneously immunized BALB/c mice. Additionally, a peptide-based vaccine, Mvac, targeting the MSP1 and AMA1 antigens was evaluated in combination with different adjuvants in an oral and subcutaneous immunization scheme applied to BALB/c mice. Adjuvants tested were plant DNA, pectin, β-subunit of cholera toxin and the GK1 peptide from T. solium. Neither plant DNA nor pectin enhanced the humoral response induced against the Mvac components. While, GK1 peptide had exerted adjuvant effects in terms of the systemic IgG responses induced against the AMA1 peptide, although pectin enhanced the IgA intestinal secretion against both MSP1 and AMA1 antigens. Overall our findings suggest that a multi-component plant-based vaccine against malaria expressing AMA1 and MSP1 antigens, and the GK1 peptide has the potential to serve as a viable and promising low-cost vaccine. As well as oral administration of a vaccine with GK1 peptide has a promising immunogenic effects, proposing that a plant-based vaccine against Malaria administered orally can be effective